May 24, 2011 -- Eating baked or broiled fish regularly may decrease the odds of heart failure in older women, new research suggests. But eating fried fish, even in small amounts, may have the opposite effect.

Researchers analyzed the self-reported diets of 84,493 postmenopausal women who participated in the Women's Health Initiative Observational Study. They found that those who ate the most baked or broiled fish -- five or more servings per week -- had a 30% lower risk of heart failure, compared to those who ate it less than once a month. In the study, eating fish included shellfish.

The scientists note that previous research has found that fatty acids in fish, called omega-3 acids, may reduce risk of cardiovascular disease by decreasing inflammation and improving blood pressure and heart and blood vessel function.

This study shows an association between eating fish and heart failure risk, but it is not designed to show cause and effect.

Type of Fish Affects Heart Risk

The study also found that the type of fish eaten may affect the risk of heart failure. Dark fish, such as salmon, mackerel, and bluefish, was associated with a significantly greater risk reduction than tuna or white fish, such as sole, snapper, and cod.

The study showed that even one serving a week of fried fish was found to be associated with a 48% higher risk of heart failure.

"Not all fish are equal, and how you prepare it really matters," study researcher Donald Lloyd-Jones, MD, ScM, of Northwestern University, says in a news release. "When you fry fish, you not only lose a lot of the benefits, you likely add some things related to the cooking process that are harmful."

Previous research has shown that frying increases trans fats in foods, which is associated with increased heart disease risk.

But in the new analysis, an observational study, no association was found between trans fats and heart failure risk.

The analysis was based on data from 1991 through August 2008. During an average follow-up of 10 years, 1,858 cases of heart failure had occurred.

Benefits of Fish

Participants whose diets included more baked or broiled fish tended to be healthier and younger than those who ate fried fish. They also were more physically active and fit, more educated, and less likely to smoke, have diabetes, high blood pressure, and heart disease.

In addition, their diets included more fruits and vegetables, more beneficial fatty acids, and less unhealthy saturated and trans fatty acids.

"Baking or broiling fish and eating it frequently seem to be part of a dietary pattern that is very beneficial for a number of things," says Lloyd-Jones, who is an associate professor at Northwestern's Feinberg School of Medicine. "In this case, we demonstrated that it's associated with heart failure prevention. This suggests that fish is a very good source of lean protein that we ought to be increasing as a proportion of our diet and decreasing foods that contain less healthy saturated and trans fats."

The American Heart Association recommends eating at least two 3.5-ounce servings of fish, particularly fatty fish, per week.

The study is published in Circulation: Heart Failure, a journal of the American Heart Association.